Dial instrument case



Jan. 27, 1942. Q H GRAESSER ETAL '2,271,423

DIAL INSTRUMENT CASE 3 Sheets-Sheet l Filed Aug. 14. 1940 Merzor.;

Jan. 27, 1942. I C, H, GREssE-R ETALy 2,271,423

DIAL INSTRUMENT CASE "Filed Aug. 14, 1940 :s sheets-sheet 2 vJim 27, 1942' l c. H. GRAEsL-:R 4le-r DIAL INSTRUMENT CASE Filed Aug. 14, 1940 3 Sheets-Sheet 3 Patented Jan. 27, 1942 y DIAL INSTRUMENT CASE Carl H. Graesser, Bridgeport, and Frank H.

Hopkins, Fairfield, Conn., assignors to Maxwell & Moore, Incorporated, New

York;

' N. Y., a corporation of New Jersey Application August 14, 1940, Serial No. 352,538l s claims. (ci. vs -151) This invention relates to pressure gauges, dial thermometers, or instruments of generally similar construction wherein a pointer or index is moved over a graduated' dial by mechanism housed within a protective casing, the latter having a removable transparent front panel, and relates' more especially to a novel form of case for such instruments. y

In accordance with usual prior practice the gauge case is a substantially cylindrical metal box, usually having a thin, integral, radial attaching flange at its rear end and having screw threads'at its forward end for engagement by screw threads formed upon'an annulus designed to be removably secured by such screw threads to the case proper, and which constitutes .a portion of the closure cap which covers and protectsthe dial and pointer. Usually, the cap includes a transparent panel of glass or the like fixed within the annulus by means Aof a screw-threaded ring which ts within the annulus and presses the glass firmly against a radial shoulder of the annulus. To provide this shoulder and to furnish a good bearing for the glass, the annulus usually has a radial ilange of substantial width whose inner edge defines the sight opening through which the dial may be viewed. Since this flange is of substantial width, for example three-eighths'of as respects the cap annulus, -requires the radial flange to be of even greater depth than usual, thus cutting off still more of the effective area of the dial.

The closure cap is usually designed for removal from the case to facilitate inspection or recalibration of the gauge mechanism. However, when the case and the bezel which holds the transparent panel are both of metal, they are subject to corrosion or rusting so that removal may become diillcult or impossible; if the case and the bezel portion of the cap are both moulded from .non-metallic material, it is diflicult so to mould an inch or more, the sight opening is of substantially less diameter than the interior of the case and thus, even though the dial .be of the maximum diameter which will ne within the case, f the effective area of the dial is .very substantially A reduced by the ange of the cap.

As noted, gauge cases have customarily been made of metal, for instance steel or brass, but some of the more recently developed plastic ma- `terials, for instance some of the synthetic resins,

have properties (for instance, ease of moulding to exact shape, lightness of weight, resistance to corrosion, fine appearance, etc.) which recommend them for use in making gauge cases. However, such materials'are not as strong as metal and if moulded to the same dimensions as the usual metal case,- the attaching flange and cap annulus would not be strong enough to withstand the stresses of use.l Thus,- heretofore, in designing gauge cases to be made from such material, it has been thought necessary to make certain parts at least of the case, for example the attaching flange and the cap annulus, of substantially greater dimensions than when these parts are made of metal. However, this imparts a clumsy appearance to the gauge, requires an abnormal amount of a 'relatively expensive material, and.

them as to provide proper tolerances or to pre-- vent subsequent plastic flow of the material, thus making it difcult to assemble the parts or to separate them.

The principal'object of the present invention is to provide a gauge case of such shape and construction that substaitially the entire dial is exposed to view; to provide a gauge case which may be made, for example, from one of the plastic non-metals but which will have adequate strength to withstand distortion by reason of the stresses imposed during use, although without undue increase in weight and at the same a pleasing external appearance; and to provide a case having provision for securing it to a support without resort to the usual radial attaching flange.

Other and further 'objects and advantages of the invention will be pointed out hereinafter in the following more detailed description and by reference to the accompanying drawings, wherein:

Fig. 1 is a front elevation of a pressure gauge embodying certain featuresof the present invention, a portion of the transparent front panel vbeing broken away:

Fig'. 2 is a vertical section substantially on the line 2-2 of Fig. `1; v

, Fig. 3 is a rear elevation of the device of Fig. l;

Fig. 4 is a fragmentary section, to larger scale, through the forward portion of the case, the transparent panel and the retaining means therefor being omitted;

Fig. 5 is a fragmentary the line 5-5 of Fig. 3;

Fig. 6 is a sideelevation of .the case;

Fig. I is a fragmentary section, similar to Fig. 2, but illustrating a modification;

Fig. 8 is a front elevation of a gauge of modified and preferred construction, portions of the section substantially on dial and the transparent panel and the parts time providingv which hold the latter in position being broken away;

Fig. 9 is a vertical diametrical section through the gauge of Fig. 8;

Fig. 10 is a fragmentary section on substantially the same plane as Fig. 9, but to much larger scale, showing the forward portion of the gauge case;

Fig. lllis aview similar to Fig. 10 but showing the transparent panel in place;

Fig. 12 is a fragmentary front view of the compression ring used in positioning the transparent panel;

Fig. 13 is a fragmentary section, substantially on the same plane as Fig. 9, but to larger scale, showing details of the split, panel retaining ring at the point where its ends abut;

Fig. 14 is a fragmentary front elevation of the parts shown in Fig. 13; and

Fig. l is a perspective view illustrating a compression ring of a modified and preferred form.

The gauge case disclosed in the drawings is designed to be molded as an integral unitary structure from a suitable plastic material, for example one of the synthetic resins, a cellulose derivative or a rubber compound, and is shown as comprising. the rear wall I and the side wall 2. The case, las here illustrated, is of substantially circular contour in front elevation, although it is to be understood that the invention is not limited to a case of this particular contour.

As shown in Fig. 2, the case increases in diameter from its front edge 3 yto a point spaced a short distance forward of its rear face 4 so that the external surface 5 of the forward, main part of the case is substantially that of a truncated cone, the exterior surface 5 flaring rearwardly from the front edge 3 and being substantially smooth and devoid of any appreciable projections or other protuberances. The'rear portion of the case,between the point 2b and the rear face 4 is substantially cylindrical, but the cylindrical and conical surfaces preferably merge in a smooth curve (Fig. 5).

As here illustrated ythe inner surface 3 of the side wall of the case is of substantially cylindrical contour, being of approximately the same diameter throughout the main part of the case -tion or displacement of the case the position of the dial.

The inner surface of theforward part of the does not aect side wall of the case is furnished with a circumferential recess or rabbet I1 (Fig. 4) providing a Aradial abutment shoulder I8 against which rests the margin of a transparent panel 20. This transparent panel is of a diameter such that its edge I9 (Fig. 2) fits snugly within the rabbet I1, the edge I9 vbeing thus located intermediate the inner andvouter surfaces of the side wall of the casing.l

Forwardly of the rabbet I1, but to the rear of the front edge 3, the inner surface of the side wall of the case is furnished with a circumferential groove 2| designed to receive a split resilient retaining ring 23 (Fig. 2), this ring being split as shown at 24 (Fig. l) to permit it to be snapped into the recess 2l. When so positioned, the ring 23 engages the outer face of the transparent panel 20 and' retains it in position against the shoulder' I8. As shown in section in Fig. 4, the peripheral wall 2| of the groove 2l flares rearwardlyso that when the resilient ring 23 has been snapped into place, it reacts against this sloping wall so as to exert rearward pressure against the panel, whether the latter be thick or thin. Preferably the inner surface of the side wall of the case, between the groove 2I and the edge i. is made to flare forward slightly tofacilitate the entry of the ring 23 into the recess 2I. It will be noted that the ring 23 is of wire of such diameter that the ring, when in place. is disposed wholly within the thickness of the side wall of the case and engages only the extreme edge portion of the transparent panel 20.

With this construction the sight opening through the transparent panel is of a diameter at least as great as that of the inner surface 6 ofthe case and is thus obviously of as great an area as that of the dial, even though the dial be as large and thus providing a substantially cylindrical chamber for the reception of the operating mechanism. As here illustrated, the lower part of the wall of the case is furnished with an aperture 1 to accommodate the socket 3 by means of which the gauge is connected to the pressure sup-i ply pipe. Obviously, the socket may be arranged to enter an opening in the rear wall I, instead of the side wall, in accordance with a usual practice. As illustrated herein,the lower part of the case in which the aperture 1 is formed is flattened or slabbed off as shown at 1*, but this is not an essential or necessary feature.

The movement frame 9 is secured within the case by means of screws I3 and supports the Bourdon tube II which, in the usual manner, by means of gauge movement mechanism, operates the index or pointer stall I2, upon the forward end of which is mounted the index or pointer I3. The movement frame also comprises posts Il and, as here illustrated, a bracket I5 fixed to and extending upwardly and forwardly from the frame 9, designed to support the graduated dial I8 in a plane substantially parallel to the plane of lthe front edge 3 of the case. The dial is thus supported independently of the case so that distoras may possibly be fitted within the case. Thus the entire area of the dial is free for observation, permitting the use of graduations disposed, if desired, at the extreme margin of the dial. In this way it is possible to space the graduations farther apartfor a given diameter of the dial than is possible when the outer part of the dial is obscured. as it is in most prior gauges by parts of the removablelcap. Thus a user might obtain the same degree of visibility by the use of a gauge of a size smaller than he customarily employed, or improved visibility when employing his accustomed size of gauge.

In order that the gauge case may not be unduly heavy, it is preferred, as illustrated in Figs. 3 and 5, to make the rear portion at least of the side wall of the case hollow. Thus, as shown in Fig. 5,' the rear part of the side wall comprises the inner portion 2' which merges integrally with the rear wall I, and the outer part 2f, which is concentric with the part 2 and whichmerges with the latter substantially midway the depth of the gauge to form the unitary forwardportion 2 of the side wall. The parts 2* and 2f. are preferably united at intervals by webs 25 (Fig. 3) to ensure the desired stiffness of construction.

-The side wall of the gauge is also furnished with a plurality of rearwardly extending niches 23 having bottom walls 21 provided with apertures 23 through which screws or bolts may be passed for securing the gauge with its rear wall I against a suitable support. With this construction, the material through which the apertures 28 pass performs the function of the usual these portions 21 of material in which the aper-l tures 28 are forme are quite short circumferentially, and are integral on three sides at least with the material of the wall of the gauge, they afford ample strength for holding the retaining bolts or screws without danger of cracking or breaking .out even though the gauge case be made of one of the plastic materials above described. Moreover, since the surfaces. 21 are within the boundaries of the case proper and form the bottoms of the niches' 26, the bolt heads are very inconspicuous (even though not wholly concealed) and do not appreciably detract from the appearance of the gauge whenin place.

While in Figs. 2 and 9 the transparent panel 20 has been shown as a flat plain panel, it lis contemplated that a panel of concavo-convex form may be employed if desired. Such an arrangement is illustrated in Fig. 7 by way of example where the concave-convex panel 20B has its edges held against an abutment shoulder by a snap ring 23. By such an arrangement as that of Fig. 7 it is posssible to decrease the front-to,- rear depth of the case substantially since it becomes practical to put the dial very close to the front of the case and to locate the index or pointer within the concavity of the transparent panel 20H.' for viewing the dial is provided, since the margin of the dial is not obscured by the Iside wall of the case even though viewed froma point substantially out of line with the axis of the index staff I2.

In the modified and preferred construction illustrated in Figs. 8 to 14 inclusive, the case is in general substantially like that above described,

being of such design that it may be moulded from-a suitable plastic material, for instance a.. and' yet having suflicientl synthetic resin,y strength and resistanceto distortion to make it acceptable for its intended use.` Likewise the case has a smooth exterior surface whose several drical chamber for the receptioniof the operaty ing mechanism. i

As illustrated in Fig. 9, the cylindrical inner surface 6 .of the side Wall of the case preferably merges with a smooth curve at 6x with the interior surface of the rear wall of the case, such Thus an even wider angle of vision the usual manner operates the index or pointer stai! I2, upon the forward end of which is e mounted the index or pointer I3. As above described, the movement frame also comprises posts or the like to which the dial I6 is secured, the dial having a three-point support wholly independent of the case.

The inner surface of the forward part of the side wall 2m of the case is furnished with a circumferential recess or rabbet I1m (Fig. 10) having a substantially vertical or radial re`ar wall I8m whose outer part also forms the rear wall of a circumferential groove 30. Spaced` forwardly vfrom the groove 36 is a secondcircumferential groove 3l whose front wall is substantially radial or vertical. The grooves 30 and 3 /I are separated by a portion 33 of the side wall 2m of the case whose inner peripheral surface 33' is su stantially cylindrical, and whose front-to-rear ength is preferably slightly less than the thickness of any glass or other transparent panel which may be used in the front of the gauge.

Within the groove 3IIis arranged a compression ring 34 (Fig. 11) This ring is made of resilient material, for example spring steel or spring brass; is preferably provided with circumferen tially spaced radial slots 35 (Fig. l2) to increase its resiliency in a radial direction; and is dished so that its inner margin tends to lie in a plane forwardly of that of its outer margin. This ring is of an outerv diameter substantially greater than the diameter of the surface 33, but by reason of its resiliency may be twisted sufficiently to snap it into the groove 30, where it may remain during the lifeof the gauge.

Fig. 15 Aillustrates another and preferred form ofvcompression ring. This ring 34* is made of resilient metal ribbon bent edgewise to circular form and having beveled ends which abut at 31. 'I'his ring is crimped or waved transversely so that when seated in grove 30 it exerts re'- `silient pressure against the panel 20m at spaced points. y

A retaining ring 36 is normally arranged within the groove 3l. This ring 36 is not necessarily as resilient as the ring 34, and as shown in Fig. 11 is substantially thicker than the ring 34, but is split at the point 31 (Fig. 14)` so that its ends at the split may be slid vby each other, thereby to decrease its external diameter sufficiently to en'- able it to be disposed in the g'roove 3 I. Preferably the outer diameter of the ring 36 is slightly greater than the outerdiameter of the groove 3l so that in order to abut the ends of the ring 36 after it has been put in place, it is necessary to impart substantial tension to the ring, thus tending to buckle it slightly out-of a plane. Preferrear wall preferably having a forward offset 6l v to which the movement frame is secured, the offsetvproviding clearance between the upper. portion of the frame and the rear wall of the case.

The lower part of the side wall of the case is furnished with an aperture 1m to accommodate the socket 8 by means of which the gauge is connected to thepressure supply pipe. As herein illustrated, the lower part of the side wall of the case, at the point where the aperture 1m is located, is flattened or slabbed off, asshown at 1n (Fig. 8).

The operating mechanism Vis substantially identical with that illustrated in Fig. 2. The movement frame 3. is secured against the offset 6* of the rear wall of the case by means of screws I0 and supports the Bourdon tube II, which in ably end portions of the ring 36, adjacent to the split 31, are turned forwardly to provide lugs 3l ,designed for engagement by a tool, for example a screw driver, to facilitate removal of the ring from the groove 3l. The inner diameters of the rings 34 and 36 are preferably substantially the same as the diameter of the dial I6 so that when the rings 34 and 36 are in place, substantially all of the dial is exposed to view. Thus the entire surface of the dial is available for the reception I of graduations or other indicia.

The transparent panel 20m which may be of glass or other suitable material is of -a diameter A preferably slightly less than the diameter of the surface 33, but isof a diameter greater than the inner diameters ofthe rings 34 and 36. This transparent panel 20m is disposed against the ring 34, the latter being seated in the groove 30,

against the transparent panel. By reason of the 5 dished shape and resilient character of the ring 34, the latter bears at all times with spring pressure against the panel m so as to prevent the latter from rattling and also to compensate for panels of substantially different thickness. Since 1o the edge of the transparent panel is disposed between the rings 34 and 36, it is wholly concealed and thus any slight roughness of such edge is immaterial. Moreover, if it be desired to associate gaskets with one or both of the rings 34 15 and 36, the overlap of the rings about the margin of the panel permits the introduction of such gaskets without detracting from the appearance of the instrument. It may be noted that in the devices of Figs. 2 20 and 9 the means for removably retaining the transparent panel in place is such as not to overlap vthe exterior surface of the case, nor even does-it cover or require any alteration in the configuration of the forward edge 3 of the case. 25

Thus the outer surface and the vforward edge of the case may be given such shape and form as may be desired to insure a good appearance, without reference to the means for securing the transparent panel in position. -Thus when, as

herein illustrated, the outer surface of the case tapers forwardly with a smooth more or less, conical surface terminating at theforward edge 0L the case, the case has a very pleasing appearance and seems smaller and less cumbersome 35 than the usual'g'auge wherein the transparent panel is held in place by a bezel ring which covers the forward edge and overhangs the outer surface of the case.

While certain desirable embodiments of the in- 40' and all equivalent constructions falling within the 'scope of the appended claims.

We claim:

l. A moulded, non-metallic, flangeless instrument case having a truncated-conical, forwardly *tapering and smooth external contour, the rear part at least of the side wall of the case com prising spaced concentric portions united at intervals by integral webs.

2. A non-metallic. flangeless instrument casel having truncated-conical forwardly tapering and smooth external contour, the rear part of the side wall of the case comprising spaced concentric portions, the rear wall of the case being 'integral' with'the inner one of said concentric portions, said concentric portions of the side wall merging at a point intermediate the rear and front faces of the case to form a wall portion of single thickness.

3. A non-metallic, angeless instrument case having a side wall which increases in thickness from front to rear, the side wall having a smooth external surface devoid of vprojections and having therein a fastener-receiving niche extending v from frontto rear and having an apertured bottom wall for the reception of a fastener.

4. A non-metallic, fiangeless instrument case having a truncated and smooth conical external contour, the rear end of the case being of greater diameter than the front, the interior of the case being of substantially uniform transverse dimensions from front to rear and the wall thickness increasing rearwardly, the wall having therein rearwardly extending niches yin its outer surface for the reception of attaching 4elements, said niches having apertured rear end walls.

5. A unitary, moulded instrument case whose exterior surface tapers forwardly from a point near its back wall to its forward edge, the front edge of the case being thin and smoothly rounded, the side wall of the case increasing in radial thickness rearwardly from said edge and having niches in its thicker rear portion for lthe reception of attaching elements, the outer surface of the case being smooth and free from iianges or projections and the case having thereinV a substantially cylindrical chamber for the reception of the gauge movement, the thin front portion of the wall of the case having an internal recess providing for disposal of the edge of a transparent panel and k of panel-retaining means in l a plane behind the plane of the front edge of the CARL H.- GRAEssER. FRANK H. HOPKINS. 

